Surgical stapling device with firing lockout member

ABSTRACT

A surgical stapling device includes a tool assembly and a drive assembly. The tool assembly includes an anvil assembly, and a cartridge assembly that includes a channel member and a staple cartridge. The staple cartridge includes a cartridge body, staples, pushers, and an actuation sled. The drive assembly has a working member that is movable through the tool assembly to advance the actuation sled through the staple cartridge and actuate the tool assembly. The anvil assembly supports a lockout member that interacts with the drive assembly when the actuation sled is not positioned in a proximal portion of the cartridge body to prevent advancement of the drive assembly and firing of the stapling device.

FIELD

The disclosure is directed to surgical stapling devices and, more particularly, to surgical stapling devices having lockout mechanisms to prevent firing of the stapling device when the stapling device has a spent staple cartridge or when an actuation sled is not present in the staple cartridge.

BACKGROUND

Surgical stapling devices for simultaneously stapling and cutting tissue are well known in the art and include a tool assembly and a drive assembly. The tool assembly includes an anvil assembly and a cartridge assembly that are movable in relation to each other between open and clamped positions. The cartridge assembly has a channel member and a staple cartridge that is received within the channel member. Typically, the staple cartridge includes a cartridge body that supports staples, pushers, and an actuation sled. The actuation sled is movable through the cartridge body from a retracted position to an advanced position into sequential engagement with the pushers to sequentially eject the staples from the cartridge body.

In some stapling devices, a knife is supported on the actuation sled and is movable with the actuation sled through the cartridge body. The drive assembly is positioned proximally of the actuation sled and is movable in relation to the anvil and cartridge assemblies to advance the actuation sled and knife through the staple cartridge to move the tool assembly between open and clamped positions, to eject the staples from the cartridge body, and to cut tissue clamped between the anvil and cartridge assemblies. When a stapling device is fired with a spent staple cartridge or a staple cartridge that does not have an actuation sled and/or a knife present in the staple cartridge, staples will not be ejected from the staple cartridge and/or tissue will not be cut.

A continuing need exists for a lock mechanism of simple construction that can prevent advancement of a drive assembly of a stapling device through the staple cartridge when a sled and/or knife is not present in a proximal portion of the staple cartridge.

SUMMARY

This disclosure is directed to a surgical stapling device that includes a tool assembly having an anvil assembly, and a cartridge assembly that has a channel member and a staple cartridge. The staple cartridge includes a cartridge body, staples, pushers, and an actuation sled. The drive assembly has a working member that is movable through the tool assembly to advance the actuation sled through the staple cartridge to actuate the tool assembly. The anvil assembly supports a lockout member that interacts with the drive assembly when the actuation sled is not present within a proximal portion of the staple cartridge to prevent advancement of the drive assembly and firing of the stapling device.

Aspects of this disclosure are directed to a surgical stapling device including an elongate body, a tool assembly, and a drive assembly. The elongate body has a proximal portion and a distal portion. The tool assembly is supported on the distal portion of the elongate body and includes an anvil assembly and a cartridge assembly. The cartridge assembly has a channel member and a staple cartridge. The channel member defines a recess that receives the staple cartridge. The staple cartridge includes a cartridge body, an actuation sled, pushers, and staples. The cartridge body defines a central knife slot and staple receiving pockets. Each of the staple receiving pockets receives one of the pushers and one of the staples. The actuation sled includes a central portion that has an abutment member and is movable through the cartridge body from a retracted position to an advanced position to sequentially eject the staples from the cartridge body. The anvil assembly is coupled to the cartridge assembly such that the tool assembly is movable between open and clamped positions. The anvil assembly includes an anvil body that defines a channel and a lockout member that is movable from a locked position extending into the channel to an unlocked position located outside the channel. The drive assembly is movable between a retracted position and an advanced position and includes a flexible drive beam and a working member. The working member is supported on a distal portion of the flexible drive beam and includes a first beam, a second beam, and a vertical strut that connects the first beam to the second beam. The drive assembly is movable from a retracted position to an advanced position to move the actuation sled from its retracted position to its advanced position. The first beam of the working member is movable through channel of the anvil assembly as the drive assembly is moved from its retracted position to its advanced position, and the locking member is positioned to obstruct movement of the drive assembly from its retracted position towards its advanced position when the lockout member is in its locked position.

In aspects of the disclosure, the abutment member of the actuation sled is positioned to engage the lockout member when the actuation sled is in its retracted position and the tool assembly is moved to the clamped position to move the lockout member from its locked position to its unlocked position.

In some aspects of the disclosure, the lockout member is supported in cantilevered fashion on the anvil body.

In certain aspects of the disclosure, the lockout member includes a proximal portion that defines a stop surface.

In aspects of the disclosure, the first beam of the working member defines a cutout that receives the distal portion of the lockout member when the actuation sled is not present in the proximal portion of the cartridge body.

In some aspects of the disclosure, the anvil assembly includes an anvil cover that is positioned over and encloses the channel.

In certain aspects of the disclosure, the lockout member is integrally formed with the anvil cover.

In aspects of the disclosure, the stapling device includes a handle assembly that is coupled to the proximal portion of the elongate body.

In some aspects of the disclosure, the flexible drive beam of the drive assembly is formed from laminated sheets of material.

In certain aspects of the disclosure, the cartridge assembly is coupled to the anvil assembly and to the elongate body to pivot in relation to the anvil assembly and the elongate body.

In aspects of the disclosure, the actuation sled includes a vertical portion that extends upwardly from a proximal portion of the central portion of the actuation sled through the central knife slot of the cartridge body.

In some aspects of the disclosure, the vertical portion supports a knife.

In certain aspects of the disclosure, the abutment portion of the actuation sled extends distally from the vertical portion above the central knife slot of the cartridge body.

Other aspects of the disclosure are directed to a tool assembly including a cartridge assembly and an anvil assembly. The cartridge assembly has a channel member and a staple cartridge. The channel member defines a recess that receives the staple cartridge. The staple cartridge includes a cartridge body, an actuation sled, pushers, and staples. The cartridge body defines a central knife slot and staple receiving pockets. Each of the staple receiving pockets receives one of the pushers and one of the staples. The actuation sled includes an abutment member and is movable through the cartridge body from a retracted position to an advanced position to sequentially eject the staples from the cartridge body. The anvil assembly is coupled to the cartridge assembly such that the tool assembly is movable between open and clamped positions. The anvil assembly includes an anvil body that defines a channel, and an anvil cover that is positioned over and encloses the channel. The anvil cover supports a lockout member that is movable from a locked position extending into the channel to an unlocked position located outside the channel.

Other aspects of the disclosure are directed to an anvil assembly that includes an anvil body and an anvil cover. The anvil body defines a channel. The anvil cover is secured to the anvil body and supports a lockout member. The anvil cover is positioned over and encloses the channel. The lockout member is coupled to the anvil cover in cantilevered fashion and is movable from a locked position extending into the channel to an unlocked position located outside the channel.

Other features of the disclosure will be appreciated from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects of the disclosure are described herein below with reference to the drawings, wherein:

FIG. 1 is side perspective view of a stapling device according to aspects of the disclosure including a tool assembly in an open position;

FIG. 2 is an enlarged view of the indicated area of detail shown in FIG. 1 illustrating the tool assembly of the stapling device shown in FIG. 1 ;

FIG. 3 is an exploded view of the anvil assembly of the tool assembly shown in FIG. 2 ;

FIG. 4 is an enlarged view of the indicated area of detail shown in FIG. 3 ;

FIG. 5 is a side perspective view of the tool assembly shown in FIG. 2 with a staple cartridge of a cartridge assembly of the tool assembly separated from a channel member of a cartridge assembly of the tool assembly;

FIG. 6 is a side perspective exploded view of the staple cartridge shown in FIG. 5 ;

FIG. 7 is an enlarged view of the indicated area of detail shown in FIG. 5 ;

FIG. 8 is an enlarged view of the indicated area of detail shown in FIG. 6 illustrating an actuation sled of the staple cartridge;

FIG. 9 is a side perspective of a distal portion of a drive assembly of the stapling device shown in FIG. 1 ;

FIG. 10 is a cross-sectional cutaway view taken along section line 10-10 of FIG. 5 ;

FIG. 11 is a cross-sectional cutaway view taken along a longitudinal axis of the tool assembly shown in FIG. 2 with the tool assembly in an open, pre-fired position;

FIG. 12 is a cross-sectional cutaway view taken along the longitudinal axis of the tool assembly shown in FIG. 2 with the tool assembly in a clamped position;

FIG. 13 is a cross-sectional cutaway view taken along the longitudinal axis of the tool assembly shown in FIG. 2 with the tool assembly in a partially fired position;

FIG. 14 is a cross-sectional cutaway view taken along the longitudinal axis of the tool assembly shown in FIG. 2 with the tool assembly in the clamped position after the stapling device has been fired and the drive assembly has returned to its retracted position; and

FIG. 15 is a cross-sectional view taken along section line 15-15 of FIG. 14 .

DETAILED DESCRIPTION

The disclosed surgical stapling device will now be described in detail with reference to the drawings in which like reference numerals designate identical or corresponding elements in each of the several views. However, it is to be understood that aspects of the disclosure are merely exemplary of the disclosure and may be embodied in various forms. Well-known functions or constructions are not described in detail to avoid obscuring the disclosure in unnecessary detail. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the disclosure in virtually any appropriately detailed structure.

In this description, the term “proximal” is used generally to refer to that portion of the device that is closer to a clinician during use of the stapling device in its customary manner, while the term “distal” is used generally to refer to that portion of the device that is farther from the clinician during use of the stapling device in its customary manner. In addition, the term “clinician” is used generally to refer to medical personnel including doctors, nurses, and support personnel. Further, directional terms such as front, rear, upper, lower, top, bottom, and similar terms are used to assist in understanding the description and are not intended to limit the disclosure.

The disclosed surgical stapling device includes a tool assembly including an anvil assembly, a cartridge assembly, and a drive assembly. The cartridge assembly has a channel member that defines a recess and a staple cartridge that is received within the recess. The staple cartridge includes a cartridge body, staples, pushers, and an actuation sled. The drive assembly has a working member that is movable through the tool assembly to advance the actuation sled through the staple cartridge to actuate the tool assembly. The anvil assembly supports a lockout member that interacts with the drive assembly when the actuation sled is not present within a proximal portion of the staple cartridge to prevent advancement of the drive assembly and firing of the stapling device.

FIG. 1 illustrates a surgical stapling device according to aspects of the disclosure shown generally as stapling device 10. The stapling device 10 includes a handle assembly 12, an elongate body 14, and a tool assembly 16. The elongate body 14 defines a longitudinal axis “X” (FIG. 1 ). The handle assembly 12 includes a body 18 that defines a hand grip 18 a, a plurality of actuator buttons 20, and a rotation knob 22. The rotation knob 22 is rotatably supported on a distal portion of the body 18 of the handle assembly 12 and supports the elongate body 14 to facilitate rotation of the elongate body 14 and the tool assembly 16 about the longitudinal axis “X” of the elongate body 14 in relation to the handle assembly 12. The actuator buttons 20 control operation of the various functions of the stapling device 10 including articulation, clamping, firing, and cutting of tissue.

The tool assembly 16 includes an anvil assembly 24 and a cartridge assembly 26 that are movable in relation to each other between open and clamped positions. As illustrated, the anvil assembly 24 is fixed in relation to the elongate body 14 and the cartridge assembly 26 is pivotable towards the anvil assembly 24. However, it is envisioned that the cartridge assembly 26 could be fixed in relation to the elongate body 14 and the anvil assembly 24 could pivot towards the cartridge assembly 26. Although the stapling device 10 is illustrated as an electrically powered stapling device, it is envisioned that the tool assembly 16 would also be suitable for use with manually powered surgical stapling devices and robotically operated stapling systems. U.S. Pat. No. 9,055,943 discloses a surgical stapling device including a powered handle assembly, U.S. Pat. No. 6,241,139 discloses a surgical stapling device including a manually actuated handle assembly, and U.S. Pat. No. 9,962,159 discloses a stapling device that is configured for use with a robotic system.

FIGS. 2-4 illustrate the anvil assembly 24 which includes an anvil cover 30 and an anvil body 32. The anvil assembly 24 can also include a dissector tip 33 as known in the art. The dissector tip 33 can be secured to or integrally formed with a distal portion of the anvil body 32. The anvil body 32 has a mounting portion 34 and an anvil portion 36 that extends along and distally of the mounting portion 34. The mounting portion 34 includes spaced extensions 38 that extend downwardly from the anvil portion 36 towards the cartridge assembly 26 and define cutouts 39. The anvil portion 36 of the anvil body 32 includes a tissue engaging surface 40 that is positioned in juxtaposed relation to the cartridge assembly 26 when the tool assembly 16 is in a clamped position (FIG. 1 ). The tissue engaging surface 40 defines a plurality of staple deforming recesses (not shown). The anvil portion 36 has a side opposite to the tissue engaging surface 40 that defines an elongated channel 46. The anvil cover 30 is secured to the anvil portion 36, e.g., by welding or crimping, to enclose the elongated channel 46 of the anvil portion 36 (FIG. 10 ). The anvil body 32 also defines a central knife slot 48 that extends through the tissue engaging surface 40 of the anvil portion 36 and communicates with the elongated channel 46 (FIG. 3 ) of the anvil portion 35.

The anvil cover 30 supports a resilient lockout member 50 that extends downwardly into the channel 46 of the anvil assembly 24. In aspects of the disclosure, the lockout member 50 has a distal end 50 a that is secured to the anvil cover 30 such as by a living hinge such that the lockout member 50 is supported on the anvil cover 30 in cantilevered fashion. It is envisioned that the lockout member 50 could be coupled to the anvil cover 30 using a variety of different types of hinges and mechanisms. In some aspects of the disclosure, the lockout member 50 is integrally formed with the anvil cover 30 and is angled downwardly in the proximal direction into the channel 46 of the anvil assembly 24. A proximal end 50 b of the lockout member 50 defines a stop surface within the channel 46 when the lockout member 50 is in a non-deformed, locked position.

FIGS. 5 and 6 illustrate the cartridge assembly 26 which includes a staple cartridge 54 and a channel member 56 that defines a recess 58 that receives the staple cartridge 54. In aspects of the disclosure, the staple cartridge 54 is releasably received within the recess 58 of the channel member 56 and is replaceable to facilitate reuse of the stapling device 10. The channel member 56 includes an angled cam surface 56 a (FIG. 11 ) and a pivot member 57 that extends outwardly from side walls of the channel member 56. The pivot member 57 is received in the cutout 39 (FIG. 3 ) of the anvil assembly 24 to pivotably couple the cartridge assembly 26 to the anvil assembly 24. In aspects of the disclosure, the cartridge assembly 26 can pivot in relation to the anvil assembly 24 between the open and clamped positions.

The staple cartridge 54 includes a cartridge body 60, an actuation sled 62, pushers 64, staples 66, and a base plate 68. The cartridge body 60 defines a central knife slot 70 and staple receiving pockets 72. In aspects of the disclosure, the staple receiving pockets 72 are aligned in rows that are positioned on each side of the central knife slot 70. Although three rows of staple receiving pockets 72 are shown on each side of the central knife slot 70, it is envisioned that the cartridge body 60 may define one or more rows of staple receiving pockets 72 on each side of the central knife slot 70. Each of the staple receiving pockets 72 receives one of the staples 66 and one of the pushers 64. The pushers 64 support the staples 66 and are engaged by the actuation sled 62 as the actuation sled 62 is advanced through the cartridge body 60 from a retracted position to an advanced position to eject the staples 66 from the cartridge body 60. The base plate 68 is secured to the bottom of the cartridge body 60 to prevent the pushers 64 and the staples 66 from falling from the cartridge body 60.

FIGS. 7 and 8 illustrate the actuation sled 62 includes a body 80 (FIG. 8 ) that has a central portion 82 and cam surfaces 84 that are positioned on opposite sides of the central portion 82 of the body 80. The cam surfaces 84 define ramps that are positioned to engage the pushers 64 as the actuation sled 62 moves from its retracted position towards its advanced position to sequentially eject the staples 66 from the cartridge body 60. The central portion 82 of the body 80 of the actuation sled 62 includes a vertical portion 86 and an abutment member 88. The vertical portion 86 of the actuation sled 62 extends upwardly from a proximal portion of the central portion 82 of the actuation sled 62 through the central knife slot 70 in the cartridge body 60 (FIG. 7 ) and includes a knife 90 that faces distally. The abutment member 88 extends distally from the vertical portion 86 of the actuation sled 62 over the knife 90 along an axis the is parallel to a longitudinal axis of the tool assembly 16 to guard or shield the knife 90. In aspects of the disclosure, the abutment member 88 extends distally from the proximal portion of the actuation sled 62 to a position above the cam surfaces 84 of the actuation sled 62.

FIG. 9 illustrates a drive assembly 100 of the stapling device 10 (FIG. 1 ). The drive assembly 100 includes a resilient and/or flexible drive beam 102 and a working member 104. The drive beam 102 has a proximal portion (not shown) that is coupled to a drive rod (not shown) supported within the elongate body 14 of the stapling device 10 (FIG. 1 ) and a distal portion that is coupled to the working member 104. In aspects of the disclosure, the resilient drive beam 102 is formed from laminated sheets 102 a of material, e.g., steel, that are welded to the working member 104. Alternately other materials of construction and securement techniques are envisioned.

The working member 104 of the drive assembly 100 has an I-beam configuration and includes a first beam 108, a second beam 110, and a vertical strut 112 that connects the first beam 108 to the second beam 110. The working member 104 is positioned proximally of the actuation sled 62 (FIG. 10 ) and is movable, in response to activation of the actuation buttons 20 (FIG. 1 ), through the tool assembly 16 between retracted and advanced positions to move the actuation sled 62 through the tool assembly 16 (FIG. 1 ) from its retracted position to its advanced position. As the working member 104 moves through the cartridge assembly 26, the first beam 108 is received within the channel 46 (FIG. 10 ) defined within the anvil assembly 24, the second beam 110 is engaged with the cartridge assembly 26, and the vertical strut 112 moves through the central knife slots 48 (FIG. 3 ) and 70 (FIG. 6 ) of the anvil portion 36 and cartridge body 60, respectively.

The first beam 108 of the working member 104 extends distally of the vertical strut 112 to form an overhang that defines a cutout 116. The cutout 116 is positioned to receive the proximal end 50 b (FIG. 4 ) of the lockout member 50 when an actuation sled 62 is not present in the proximal portion of the staple cartridge 54 to prevent advancement of the drive assembly 130 as described below.

FIGS. 10 and 11 illustrate the tool assembly 16 of the stapling device 10 in the open position. In FIG. 10 , the staple cartridge 54 (FIG. 11 ) has not been positioned within the recess 58 of the channel member 56. In this condition, the lockout member 50 is in its undeformed, locked position with the proximal end 50 b of the lockout member 50 positioned within the channel 46 of the anvil assembly 24.

In FIG. 11 , the staple cartridge 54 is received within the recess 58 of the channel member 56. In this position, the lockout member 50 remains in its undeformed, locked position with the proximal end 50 b of the lockout member 50 positioned within the channel 46 of the anvil assembly 24. The abutment member 88 of the actuation sled 62 of the staple cartridge 54 is positioned beneath the lockout member 50 of the anvil assembly 24.

FIG. 12 illustrates the tool assembly 16 of the stapling device 10 (FIG. 1 ) in the clamped position. When the drive assembly 100 is moved in the direction of arrow ‘A” from the retracted position towards the advanced position, the first beam 108 of the working member 104 is received within the channel 46 of the anvil assembly 24 and the second beam 110 of the working member 104 engages the cam surface 56 a (FIG. 11 ) of the channel member 56 of the cartridge assembly 26 to pivot the cartridge assembly 26 upwardly towards the anvil assembly 24 in the direction of arrow “B” to move the tool assembly 16 from the open position to the clamped position. As the tool assembly 16 moves towards the clamped position, the abutment member 88 of the actuation sled 62 engages the lockout member 50 to deform the lockout member 50 upwardly in the direction of arrow “C” from the locked position to an unlocked position. In the unlocked position, the lockout member 50 is moved out of the channel 46 in the anvil assembly 24 to allow passage of the actuation sled 62 and the working member 104 of the drive assembly 100.

FIG. 13 illustrates the tool assembly 16 as the drive assembly 100 of the stapling device 10 (FIG. 1 ) moves past the lockout member 50 in the direction of arrow “A” towards its advanced position. As the drive assembly 100 moves towards its advanced position, the working member 104 engages and advances the actuation sled 62 through the cartridge body 60 to eject the staples 66 from the cartridge body 60. As the actuation sled 62 moves through the cartridge body 60, the knife 90 moves through the central knife slot 70 of the cartridge body 60 to cut tissue clamped between the anvil and cartridge assemblies 24 and 26, respectively.

After the stapling device 10 is fired and the drive assembly 100 is returned to its retracted position, the actuation sled 62 remains in the distal portion of the cartridge body 60. As the drive assembly is returned to its retracted position, the first beam 108 of the working member 104 of the drive assembly 100 engages the distal portion 50 a of the lockout member 50 to urge the lockout member 50 back to its deformed, unlocked position. In the unlocked position of the lockout member 50, the working member 104 can pass by the lockout member 50 and return to its retracted position.

FIGS. 14 and 15 illustrate a tool assembly 16 in which an actuation sled 62 (FIG. 13 ) is not present in the proximal portion of the staple cartridge 54. The actuation sled 62 will not be present in the proximal portion of the staple cartridge 54 if the staple cartridge 54 has been fired or the actuation sled 62 was inadvertently not included in the staple cartridge 54 during manufacture of the staple cartridge 54. When an actuation sled 62 is not present in the proximal portion of the staple cartridge 54, the lockout member 50 remains in its locked position when the cartridge assembly 26 is moved in the direction of arrow “D” to its clamped position. When the lockout member 50 is in its locked position, the lockout member 50 extends downwardly into the channel 46 of the anvil assembly 24 such that the stop surface 50 b of the lockout member 50 obstructs advancement of the working member 104 of the drive assembly 100 through the cartridge body 60. When the drive assembly 100 is advanced with the lockout member 50 in its locked position, the stop surface 50 b of the lockout member 50 is received within the cutout 116 (FIG. 9 ) of the first beam 108 of the working member 104 of the drive assembly 100 and engages a distal face of the vertical strut 112 to prevent further distal movement of the drive assembly 100. This prevents firing of the stapling device 10 (FIG. 1 ).

Persons skilled in the art will understand that the devices and methods specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary embodiments. It is envisioned that the elements and features illustrated or described in connection with one exemplary embodiment may be combined with the elements and features of another without departing from the scope of the disclosure. As well, one skilled in the art will appreciate further features and advantages of the disclosure based on the above-described embodiments. Accordingly, the disclosure is not to be limited by what has been particularly shown and described, except as indicated by the appended claims. 

What is claimed is:
 1. A surgical stapling device comprising: an elongate body having a proximal portion and a distal portion; a tool assembly supported on the distal portion of the elongate body, the tool assembly including: a cartridge assembly having a channel member and a staple cartridge, the channel member defining a recess that receives the staple cartridge, the staple cartridge including a cartridge body, an actuation sled, pushers, and staples, the cartridge body defining a central knife slot and staple receiving pockets, each of the staple receiving pockets receiving one of the pushers and one of the staples, the actuation sled including a central portion having an abutment member and being movable through the cartridge body from a retracted position to an advanced position to sequentially eject the staples from the cartridge body; and an anvil assembly coupled to the cartridge assembly such that the tool assembly is movable between open and clamped positions, the anvil assembly including an anvil body defining a channel and a lockout member that is movable from a locked position extending into the channel to an unlocked position located outside the channel; and a drive assembly movable between a retracted position and an advanced position and including a flexible drive beam and a working member, the flexible drive beam having a proximal portion and a distal portion, the working member supported on the distal portion of the flexible drive beam and including a first beam, a second beam, and a vertical strut connecting the first beam to the second beam, the drive assembly movable from a retracted position to an advanced position to move the actuation sled from its retracted position to its advanced position, the first beam movable through channel of the anvil assembly as the drive assembly is moved from its retracted position to its advanced position, wherein the locking member obstructs movement of the drive assembly from its retracted position towards its advanced position when the lockout member is in its locked position.
 2. The stapling device of claim 1, wherein the abutment member of the actuation sled is positioned to engage the lockout member when the actuation sled is in its retracted position and the tool assembly is moved to the clamped position, engagement between the abutment member and the lockout member moving the lockout member from its locked position to its unlocked position.
 3. The stapling device of claim 2, wherein the lockout member is supported in cantilevered fashion on the anvil body.
 4. The stapling device of claim 3, wherein the lockout member includes a proximal portion that defines a stop surface.
 5. The stapling device of claim 4, wherein the first beam of the working member defines a cutout that receives the distal portion of the lockout member when the actuation sled is not present in the proximal portion of the cartridge body.
 6. The stapling device of claim 3, wherein the anvil assembly includes a cover that is positioned over and encloses the channel, lockout member being integrally formed with the cover.
 7. The stapling device of claim 1, further including a handle assembly coupled to the proximal portion of the elongate body.
 8. The stapling device of claim 1, wherein the flexible drive beam of the drive assembly is formed from laminated sheets of material.
 9. The stapling device of claim 1, wherein the cartridge assembly is coupled to the anvil assembly and to the elongate body to pivot in relation to the anvil assembly and the elongate body.
 10. The stapling device of claim 2, wherein the actuation sled includes a vertical portion that extends upwardly from a proximal portion of the central portion of the actuation sled through the central knife slot of the cartridge body.
 11. The stapling device of claim 10, wherein the vertical portion supports a knife.
 12. The stapling device of claim 11, wherein the abutment portion of the actuation sled extends distally from the vertical portion above the central knife slot of the cartridge body.
 13. A tool assembly comprising: a cartridge assembly having a channel member and a staple cartridge, the channel member defining a recess that receives the staple cartridge, the staple cartridge including a cartridge body, an actuation sled, pushers, and staples, the cartridge body defining a central knife slot and staple receiving pockets, each of the staple receiving pockets receiving one of the pushers and one of the staples, the actuation sled including an abutment member and being movable through the cartridge body from a retracted position to an advanced position to sequentially eject the staples from the cartridge body; and an anvil assembly coupled to the cartridge assembly to facilitate movement of the tool assembly between open and clamped positions, the anvil assembly including an anvil body defining a channel and an anvil cover positioned over and enclosing the channel, the anvil cover supporting a lockout member that is movable from a locked position extending into the channel to an unlocked position located outside the channel.
 14. The tool assembly of claim 13, wherein the abutment member of the actuation sled is positioned to engage the lockout member when the actuation sled is in its retracted position and the tool assembly is moved to the clamped position, engagement between the abutment member and the lockout member moving the lockout member from its locked position to its unlocked position.
 15. The tool assembly of claim 14, wherein the lockout member is supported by the cover in cantilevered fashion and includes a distal portion engaged with the anvil cover and a proximal portion defining a stop surface.
 16. The tool assembly of claim 15, wherein the cartridge assembly is coupled to the anvil assembly to pivot between the open and clamped positions.
 17. The tool assembly of claim 14, wherein the actuation sled includes a vertical portion that extends upwardly from a proximal portion of the central portion of the actuation sled through the central knife slot of the cartridge body.
 18. The tool assembly of claim 17, wherein the vertical portion supports a knife.
 19. The tool assembly of claim 18, wherein the abutment portion of the actuation sled extends distally from the vertical portion above the central knife slot of the cartridge body.
 20. An anvil assembly comprising: an anvil body defining a channel; and an anvil cover secured to the anvil body, the anvil cover supporting a lockout member and being positioned over and enclosing the channel, the lockout member coupled to the anvil cover in cantilevered fashion and being movable from a locked position extending into the channel to an unlocked position located outside the channel. 